ES2985365T3 - Method for roasting coffee beans - Google Patents

Abstract

The invention relates to an apparatus for roasting partially pre-roasted coffee beans comprising: - a container (1) for holding coffee beans, - an electric heater (13) for heating the coffee beans contained in the container, - at least one temperature sensor (23) for measuring the temperature in the container, - a control system (180) operable to control the heater, wherein the control system is configured to: - apply a roasting recipe dedicated to roasting partially pre-roasted beans comprising at least one temperature profile as a function of time, - measure the concentration of at least one volatile organic component (VOC) in the smoke produced in the container during the time in which the roasting recipe is applied, - detect an increase in the measured concentration as a function of time, - stop heating if no increase in the measured concentration occurs after a set reference time t1. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Method for roasting coffee beans

Field of invention

The present invention relates to the roasting of coffee beans with hot air and, more specifically, to the roasting of partially pre-roasted beans, preferably in relatively small quantities of coffee beans, particularly suitable for use at home or in shops and cafes.

Background of the invention

Typically, coffee bean roasting involves roasting green coffee beans. This roasting requires a certain amount of time and generates a certain amount of smoke, particularly in the first stage of roasting. Furthermore, roasting requires certain know-how to obtain the best roast from various different green beans and to match the preferences of the end customers.

As a simpler alternative to roasting green beans, it has been proposed to roast partially roasted beans. These beans have been partially roasted in a manufacturing roasting plant to a point that allows a second final roast before consumption. The first partial roast provides the advantage of shortening the final roast, which may only last a few minutes. Another advantage is that less smoke is generated during the final roast. The use of partially roasted beans has been described in patents no. WO 03/082705, US 2013/180406, WO 2015/110337, WO 2015/162021.

Thanks to this alternative, roasting becomes easier for non-roasting experts and a new range of roasting appliances can be proposed for use at home or in shops and cafes. Such roasting appliances can be automated sufficiently so that operators without roasting experience can start the roasting operation.

When a roasting appliance is set to roast only partially pre-roasted beans, there is a risk that the user may mistakenly introduce green beans into the appliance, particularly if the user is not an expert. The problem is that the heating profile for partially pre-roasted beans is different from the heating profile when starting with green beans. Using a heating profile that is not adapted to green beans has the consequence that, at the end of the roasting process, the green beans may not be sufficiently roasted, with the associated risk that these beans may damage the device used to grind the roasted beans at a later stage and that the coffee extracted from these roasted and ground beans may have a high level of acrylamide.

Similarly, when a non-skilled person operates a roasting appliance, there is a risk that the user forgets to remove the fully roasted beans from the appliance at the end of the roasting operation and starts a new roast without these already roasted beans. The consequence is that these beans can burn and cause a fire inside the appliance. It can also happen that the user starts a roasting operation with partially pre-roasted beans and stops the roasting process before it has reached its end for an unpredictable reason. The user restarts the roasting later with a new roasting cycle started from the beginning. This restarting of the roasting can lead to the fire risk mentioned above or to the problem of a roast that is not adapted to the beans, leading to a poor final quality.

Additional roasting apparatuses are known from EP 3 311 675 A1, WO 2016/063177 A1, WO 2016/083148 A1 and WO 2016/071165 A1.

Summary of the invention

An objective of the present invention is to improve the roasting of coffee beans in apparatuses that implement the roasting of partially roasted beans.

It would be advantageous to provide a roasting apparatus that avoids the risk of fire due to loading of wrong coffee beans such as green beans or fully roasted beans.

The objects of the invention are achieved by the apparatus for roasting coffee beans according to claim 1, the method of claim 8 and the computer program according to claim 10.

In the present application, “partially pre-roasted beans” means beans that have been obtained by heating green coffee beans and stopping said heating process before the end of the first crack. This definition includes beans that have been obtained by heating green coffee beans and stopping said heating process before the beginning of the first crack.

In this application, “fully roasted beans” means that the beans have been roasted after the second cracking.

In a first aspect of the invention, there is provided an apparatus for roasting coffee beans comprising:

- a container for holding coffee beans,

- a heater for heating coffee beans contained in the container,

- at least one temperature sensor for measuring the temperature in the container,

- at least one sensor for measuring the concentration of at least one volatile organic component (VOC) in the smoke produced in the container,

- a control system that can be operated to control the heater,

where the control system is configured to:

- apply a roasting recipe dedicated to roasting partially pre-roasted beans comprising at least one temperature profile with respect to time,

- measure the concentration of at least one volatile organic component (VOC) in the smoke produced in the vessel during the time the roasting recipe is applied,

- detect an increase in the measured concentration as a function of time,

- stop heating if no increase in the measured concentration occurs after a set reference time t

In the container, the coffee beans are heated and preferably mixed to homogenize the heating throughout the beans.

Mixing can be achieved with a hot air fluidized bed or mechanically with stirring paddles or by the rotation of a rotating drum.

Preferably, the vessel is a hot air fluidized bed chamber. Within such a vessel, hot air is forced through a screen or perforated plate beneath the coffee beans with sufficient force to lift the beans. Heat is transferred to the beans as they tumble and circulate within this fluidized bed. Alternatively, the vessel may be a drum chamber wherein the coffee beans are tumbled in a heated environment. The drum chamber may consist of a horizontally rotating drum or the drum chamber may comprise agitator paddles for tumbling the coffee beans in a heated environment.

As a heating source, the apparatus preferably comprises an electric heater. This electric heater usually comprises an electric resistor. Furthermore, the heater preferably comprises an air blower for circulating the air heated by the heater. In some apparatus, the air blower is not necessary, for example when the apparatus comprises stirring blades or is a rotating drum.

An electrically powered heater has the advantage that the air pollutants produced during roasting are pollutants generated by the heating of the coffee beans themselves and not by the burning of gases as occurs when the heating source is a gas burner using natural gas, propane, liquefied petroleum gas (LPG) or even wood.

The apparatus comprises at least one temperature sensor for measuring the temperature in the container. The sensor may be located within the volume of the container or near the hot air inlet into the container.

The apparatus comprises a control system operable to control the electric heater to apply a temperature profile with respect to time within the vessel. Typically, this control is implemented based on the measurement of at least one temperature sensor located in the vessel in the feedback loop control.

The temperature versus time profile corresponds to a roasting recipe dedicated to roasting partially pre-roasted beans. Usually, the time span of such a profile is shorter than the time span of the profile dedicated to roasting green coffee beans.

Furthermore, the control system is configured to measure the concentration of at least one volatile organic component (VOC), preferably at least one component from the list of: CO, CO2, NO, NO2, SO2, formaldehyde in the smoke produced in the vessel during the time the roasting recipe is applied.

Preferably, the VOC sensor is located inside the vessel or downstream of the vessel, for example at the outlet of the vessel.

The control system is configured to detect an increase in the measured concentration as a function of time.

In the preferred embodiment, the concentration of CO and/or CO2 is measured.

In the process of roasting coffee beans from green coffee beans to a roasting level that allows the preparation of a coffee drink by infusion with water, the coffee beans go through several stages and in particular through:

- a first stage in which the level of emissions remains low, then

- a first stage of cracking where internal exothermic reactions occur and components such as CO, CO2 and other VOCs are produced and emitted, then

- a second stage in which the level of emissions decreases,

- a second stage of cracking where internal exothermic reactions occur and VOCs are emitted again.

Depending on whether green beans or partially pre-roasted beans are heated, the time at which the first stage of cracking occurs is different:

- it is longer for green beans than for partially pre-roasted beans, usually at least 2 minutes,

- there is no first crack for fully roasted beans.

This means that green beans and fully roasted beans can be differentiated from partially pre-roasted beans in that, when applying the same roasting profile, the first cracking occurs later for green beans compared to partially roasted beans or does not occur at all for fully roasted beans. As a result, by establishing a reference time at which the first cracking of partially pre-roasted beans usually occurs, it is possible to detect whether indeed partially pre-roasted beans are present in the container and are being roasted.

The control system is set to stop the heater if no increase in the measured concentration of CO, CO2, ... occurs after a set reference time. Actually, by setting the reference time up to the moment when the first cracking of the partially pre-roasted beans occurs, if no decrease in consumption occurs at that moment, it means that green beans or fully roasted beans or even no beans have been introduced into the vessel. For safety, the heating is stopped. A message may be displayed to inform the operator and induce him to check the nature of the beans introduced into the vessel.

Advantageously, the objectives of the invention are solved since the prior detection of the time at which the first decrease in the consumption of electrical energy by the heater occurs makes it possible to verify the nature of the grains introduced into the container.

The reference time ti can be defined according to the nature of the partially pre-roasted beans produced for use in the roasting apparatus by applying the roasting recipe dedicated to roasting partially pre-roasted beans. Preferably, the reference time for the first increase in the measured concentration is set at 5 minutes.

In fact, it has been observed that for green grains, the first increase in measured concentration is usually at least 5 minutes.

It may be possible that the operator mistakenly introduces pre-roasted beans into the vessel up to a point between the end of the first crack and the beginning of the second crack, or forgets to remove beans from a previous roasting operation from the vessel. In that case, when applying the roasting profile, there is no first crack, but the second crack occurs very quickly after starting to heat these beans. In case of such an error, the problem of a fire is less critical than for fully roasted beans, but the final roasting does not lead to an optimized product and such roasting is not recommended. In a preferred embodiment, to avoid such roasting, the control system may be configured to stop the electric heater if the first increase in the measured concentration occurs before a set reference time to. Preferably, this reference time to may be set to 3 minutes.

In one embodiment, the control system is configured to obtain the identification of the coffee beans introduced into the container by the user. The identification of the beans is related to the nature of the beans which has a direct impact on the roasting process of the beans. Generally, the nature is related to the origin of the beans (Arabica, Robusta, ...).

Grain identification can be obtained:

- by manual input by the user,

- from an identification device configured to automatically read identification media from a package of grain presented by the user.

In all cases, the user puts the beans into the container, which explains the problem that the beans in the container may not be partially pre-roasted beans.

The control system can be configured to obtain the roasting recipe corresponding to the coffee beans identified before the step of applying the roasting recipe. The roasting recipe can be obtained:

- from a memory,

- from a server,

- from the identification device.

The foregoing aspects of the invention may be combined in any suitable combination. Furthermore, various features in the present disclosure may be combined with one or more of the foregoing aspects to provide combinations other than those specifically illustrated and described. Other objects and advantageous features of the invention will become apparent from the claims, the detailed description, and the accompanying figures.

Brief description of the figures

The features and advantages of the invention will be better understood in relation to the following figures:

- Figure 1 is a schematic drawing of a general roasting apparatus that allows the implementation of the method of the present invention,

- Figure 2 shows a block diagram of a general apparatus control system according to Figure 1,

- Figure 3 schematically represents curves of the heating profile applied to green beans and partially pre-roasted beans,

- Figure 4 schematically represents a first curve of the electric energy consumption of the heater during the roasting stage of partially pre-roasted coffee beans and a second curve of the electric energy consumption of the heater during the roasting stage of green beans.

Detailed description of the figures

Figure 1 shows an illustrative view of a roasting apparatus 1. Functionally, the roasting apparatus 1 can be operated to roast coffee beans contained in a container 11 by means of a flow of hot air introduced into this container. At a first level, the apparatus comprises: a housing 15, a roasting unit 10 and a control system 180. These components will be described sequentially below.

Housing of the toaster appliance

The housing 15 houses and supports the aforementioned components and comprises a base 151 and a body 152. The base 151 is for abutting a supporting surface, preferably through feet 154 which provide a space between the base and the supporting surface. The body 152 is for mounting the components thereon.

Toaster unit of the toaster appliance

The roasting unit 10 can be operated to receive and roast coffee beans.

The toaster unit 10 typically comprises, on a second level of the toaster apparatus 1: a container 11, an air flow impeller 12, a heater 13, which are described sequentially.

The container 11 is configured to receive and contain coffee beans introduced by the operator. A removable cover 17 allows beans to be introduced and removed. The bottom of the container is configured to allow air to pass through, specifically it may be a perforated plate 14 on which the beans can lie and through which air can flow upwards.

A husk collector 16 is in continuous communication with the container 1 to receive husks that are progressively separated from the grains and due to their low density are expelled towards the husk collector.

The container 11 comprises a handle 112 to allow the user to remove the container from the housing 15 and obtain the roasted beans.

The airflow impeller 12 operates to generate a flow of air in the direction of the bottom of the vessel. The generated flow is configured to heat the grains and to agitate and lift the grains, which creates a fluidized bed of air. As a result, the grains are heated homogeneously. Specifically, the airflow impeller may be a fan driven by a motor 121. Air inlets 153 may be provided within the base 151 of the housing to supply air into the housing, the airflow impeller blows this air in the direction of the vessel 11.

In an alternative embodiment of the roaster, not shown, the container may comprise a rotating device for rotating the beans within the container. In that case, a simple flow of air may be provided and the rotating device allows for homogeneous heating of the beans.

The heater 13 is operable to heat the air flow generated by the air flow impeller 12. In the illustrated embodiment, the heater is an electrical resistor located between the fan and the perforated plate 14 with the result that the air flow is heated before entering the container 11 to heat and lift the grains.

The heater 13 and/or the airflow impeller may be operated to apply a roasting profile to the beans, this roasting profile being defined as a curve of temperature versus time.

Toaster control system

With reference to Figures 1 and 2, the control system 180 will now be considered: the control system 180 can be operated to control components of the roasting unit for roasting coffee beans. The control system 180 typically comprises, on a second level of the roasting apparatus: a user interface 20, a processing unit 18, at least one sensor 23, a power supply 21, a memory 19, optionally a code reader, optionally a communication interface for remote connection.

The user interface 20 comprises hardware for allowing a user to interact with the processing unit 1, by means of a user interface signal. More particularly, the user interface receives commands from a user, the user interface signal transfers said commands to the processing unit 18 as an input. The commands may be, for example, information about the nature of the beans introduced into the container (such as origins, supplier reference), an instruction to execute a roasting process (start the process) and/or to adjust an operating parameter (desired final roast level, amount of beans to be roasted) of the roasting apparatus 1 and/or to switch the roasting apparatus 1 on or off. The processing unit 18 may also issue feedback to the user interface 20 as part of the roasting process, e.g., to indicate that the roasting process has been started or that a parameter associated with the process has been selected or to indicate the evolution of a parameter during the process or to create an alarm.

The user interface hardware may comprise any suitable device, for example, the hardware comprises one or more of the following: buttons, such as a joystick button, push button or knob, joystick, LED, graphics or character LCD, graphical display with touch sensing buttons and/or display border. The user interface 20 may be formed as a single unit or a plurality of discrete units.

A portion of the user interface may also be in a mobile application when the apparatus is provided with a communication interface 24 as described below.

The at least one sensor 23 is operable to provide an input signal to the processing unit 18 for monitoring the roasting process and/or a status of the roasting apparatus. The input signal may be an analog or digital signal. The sensors 23 typically comprise at least one temperature sensor 231 and, optionally, one or more of the following sensors: bean level sensor associated with the container 1, position sensor associated with the container 11 and/or the husk collector 16.

In addition, the sensors 23 comprise a sensor 232 for measuring the concentration of at least one VOC component. This sensor 232 is usually located at the outlet of the vessel. If the outlet of the vessel is connected to a flue gas treatment unit, this sensor 232 is located upstream of any filter or catalytic converter so that the measurement is not changed by the flue gas treatment.

The processing unit may comprise a code reader 3 associated with, for example, a system for reading a code on grain packaging.

The processing unit may comprise a communication interface 24 for data communication of the roasting apparatus 1 with another device and/or system, such as a server system and/or a mobile device. The communication interface 24 may be used to supply and/or receive information related to the roasting process of coffee beans, such as information on the roasting process, nature of the beans, quantity of beans. The communication interface 24 may comprise a first and a second communication interface for data communication with several devices at once or communication via different media.

The communication interface 24 may be configured for wired media or wireless media or a combination thereof, e.g., a wired connection such as RS-232, USB, I2C, Ethernet as defined by IEEE 802.3, a wireless connection such as wireless LAN (e.g., IEEE 802.11) or near field communication (NFC), or a cellular system such as GPRS or GSM. The communication interface 24 interacts with the processing unit 18 via a communication interface signal. Typically, the communication interface comprises a separate processing unit (examples of which are provided above) for controlling communication hardware (e.g., an antenna) and interacting with the master processing unit 18. However, less complex configurations may be used, for example, a simple wired connection for serial communication directly with the processing unit 18.

The processing unit 18 generally comprises memory input/output system components arranged as an integrated circuit, typically as a microprocessor or microcontroller. The processing unit 18 may comprise other suitable integrated circuits, such as: an ASIC, a programmable logic device such as a PAL, CPLD, FPGA, PSoC, a system on a chip (SoC), an analogue integrated circuit, such as a controller. For such devices, where appropriate, the above-mentioned program code may be considered programmed logic or further comprising programmed logic. The processing unit 18 may also comprise one or more of the above-mentioned integrated circuits. An example of the latter is that several integrated circuits are arranged in communication with each other in a modular manner, e.g.: a slave integrated circuit for controlling the user interface 20 in communication with a master integrated circuit for controlling the toaster unit 10.

The processing unit 18 generally comprises a memory unit 19 for storing instructions as program code and optionally data. For this purpose, the memory unit typically comprises: a non-volatile memory, e.g. EPROM, EEPROM or Flash for storage of the program code and operating parameters as instructions, volatile memory (RAM) for temporary storage of data. The memory unit may comprise a separate and/or integrated memory (e.g. on a semiconductor die). For programmable logic devices, instructions may be stored as programmed logic.

The instructions stored in the memory unit 19 may be idealized as comprising a coffee bean roasting program. The coffee bean roasting program may be executed by the processing unit 18 in response to such input as commands from the user interface 20 and/or signal from sensors 23 such as temperature sensor 231, concentration sensor 232, bean quantity or level sensor, code reader 3. Execution of the coffee bean roasting program causes the processing unit 18 to control the following components: heater 13 and air flow impeller 12.

The processing unit 18 can be operated to:

- receiving an input, i.e. commands from the user interface 20 and/or the signal from the sensors (e.g. the temperature sensor 231 associated with the container 1, the grain level sensor) and/or the code reader 3,

- process the input according to the roasting program code (or programmed logic) stored in the memory unit 19 and/or assigned from an external source such as the communication interface 24,

- providing an output, which is the roasting process. More specifically, the output comprises the operation of at least the heater 13 and/or the air flow impeller 12.

The operation of the roasting unit is usually controlled in a closed loop by using the input signal from the temperature sensor 231 as feedback to apply the temperature versus time profile to the coffee beans.

The control system 80 may be operated to implement this coffee bean roasting process by controlling the air flow impeller 12 and/or the heater 13 usually with the use of a signal from the temperature probe 231.

The temperature measured by the temperature probe 231 is used to adapt the power of the heater 13 and/or the power of the air blower 12 in a feedback loop to apply the roasting recipe R to the beans.

Depending on the type of control, the heater 13 may be supplied with a predetermined power, meaning that its temperature is constant, and in that case the power of the air blower 12 may be controlled based on the temperature monitored at the probe 231 to vary the contact time of the flowing air through the heater during its movement.

Alternatively, the air blower 12 may be supplied with a predetermined power, meaning that the air flow rate is constant, and in that case the power of the heater 13 may be controlled based on the temperature monitored at the probe 231 to heat more or less air during its passage through the heater.

In a final alternative, both the heater 13 and the air blower 12 can be controlled based on temperature monitoring by probe 231.

Part of the roasting program is based on a roasting recipe comprising a temperature versus time profile to be applied to the beans. The coffee bean roasting program is set up to roast partially pre-roasted beans.

Figure 3 illustrates the heating profiles (temperature versus time) for roasting green coffee beans (green curve) and partially pre-roasted beans of the same origin (Pre-roasted curve) in apparatus 1. t^mcio de cracking is the time corresponding to the start of the first crack, end of cracking is the time corresponding to the end of the first crack, t2inicio de cracking is the time corresponding to the start of the second crack.

As illustrated by the Tightening curve, when the beans have been partially pre-roasted, the heating profile is shorter in time: the first part of the Agreen curve is not applied, but the heating profile starts before the end of cracking. Consequently, in the roasting apparatus 1, the control system is set up to apply a roasting recipe or roasting program dedicated to the roasting of partially pre-roasted beans, as illustrated by the heating profile of the Tightening curve.

The power supply 21 may be operable to supply electrical power to said controlled components and to the processing unit 18. The power supply 21 may comprise various means, such as a battery or a unit for receiving and conditioning a main electrical supply. The power supply 21 may be operatively connected to part of the user interface 20 to turn the toaster apparatus 1 on or off.

Based on another part of the instructions stored in the memory unit 19, the processing unit 18 can be operated to:

- measure the concentration of at least one VOC component in the smoke produced in the vessel during the time the roasting recipe is applied,

- detect an increase in the measured concentration as a function of time,

- stop heating if no increase in the measured concentration occurs after a set reference time t1.

During the roasting operation, the input 230 of the concentration of at least one VOC component, preferably in the list of: CO, CO2, NO, NO2, SO2, formaldehyde, in the smoke produced in the vessel is monitored by the processing unit 18.

Based on the measurement of the concentration during the time that the roasting recipe is applied, the processing unit 18 is configured to detect an increase in this concentration as a function of time.

Preferably, the increase in concentration to be detected is sufficiently large to correspond to the production of VOC components during the first cracking of the coffee beans.

Based on the concentration monitoring, the processing unit 18 is configured to stop the electric heater if no increase in concentration occurs after a set reference time t1.

In fact, if no increase in concentration occurs within a relatively short period of time after the start of the process, this means that no partially pre-roasted beans have been introduced into the apparatus and that the container 11 contains either green beans or fully roasted beans or even no beans at all.

As illustrated by the curves in Figure 3, although the same heating profile is applied to partially pre-roasted coffee beans and green beans from the same origins (i.e. the partially pre-roasted coffee beans have been obtained from said green beans), the first cracking of the green beans occurs later than the first cracking of the partially pre-roasted coffee beans.

Figure 4 schematically illustrates the measured concentration Q of CO in the smoke produced in the vessel during heating of:

- green grains (Green Curve), and

- partially pre-roasted coffee beans obtained from the same origin as the green beans (Bpre-roasted curve) according to the heating profile (temperature versus time) of the APre-roasted curve in Figure 3. In both cases, the curve shows a peak corresponding to the emission of CO. The concentration of CO starts to increase at the moment when the first cracking of the beans occurs and continues to increase until it reaches its maximum after the second cracking.

The increase in CO concentration corresponding to the first cracking of partially pre-roasted beans occurs at time tpre-roasted, which is before time tgreen corresponding to the increase in CO concentration and the first cracking of green beans.

By setting a reference time t1 greater than tpre-roasted, but less than tgreen, it is possible to discriminate partially pre-roasted beans from green beans. Generally (but it may depend on one type of partially pre-roasted beans to another), the reference time t1 is set at 5 minutes.

If fully roasted beans that were roasted until after the second cracking were introduced into the vessel instead of partially roasted beans, then no increase in CO concentration would be detected before or after time t1 in a similar way to the green beans.

If roasted beans have been introduced up to a point between the end of the first crack and the beginning of the second crack, then the emission of Co which is prior to tpre-roasting would be immediately detected. Consequently, by setting a reference time tü shorter than tpre-roasting, it is possible to discriminate these beans from partially pre-roasted beans. Generally (but it may depend on one type of partially pre-roasted beans to another), the reference time tü is set at 3 minutes.

Finally, depending on the type of beans identified in the container, the control system is configured to continue or stop the heater 13.

If the beans are identified as partially pre-roasted beans, heating can be carried out according to the roasting recipe.

If the beans are identified as green beans or fully roasted beans, heating is stopped and an alert is sent to the user, for example, via the user interface 20.

As a result, the user introduces beans into the container and can supply information about their type to the processing unit in the most advanced mode (either manually or automatically with a code). However, whatever the mode, since the beans are introduced manually into the container, there is a risk that the user does not introduce partially pre-roasted beans into the container and, in particular, forgets to remove fully roasted beans from a previous operation or introduces green beans into the container.

The apparatus of the present invention has the advantage of avoiding any risk of fire due to user carelessness without implementing complex and expensive devices.

In the step of applying a roasting recipe comprising at least one temperature versus time profile by controlling the electric heater and/or the airflow impeller based on the measurement of the temperature sensor, the roasting recipe may be a predetermined recipe for roasting partially pre-roasted beans or it may be a recipe dedicated to the partially pre-roasted beans identified in the optional identification step and derived from an optional step to obtain the dedicated roasting recipe for these identified beans.

This dedicated roasting recipe can be obtained from the memory unit 19 of the roasting apparatus or can be downloaded from a server via the communication interface 24 or read by the code reader during the optional code reading step, the recipe being part of the information related to the identification of the beans.

Although the invention has been described with reference to the embodiments illustrated above, it will be appreciated that the claimed invention is in no way limited by these illustrated embodiments.

As used in this specification, the words “comprises,” “comprising,” and similar words are not to be construed in an exclusive or exhaustive sense. In other words, they mean “including, but not limited to.”

List of references in the figures:

toaster 1

roasting unit 10

container 11

handle 112

fan 12

engine 121

heater 13

perforated plate 14

accommodation 15

base 151

body 152

air inlet 153

feet 154

shell collector 16

cover 17

processing unit 18

control system 180

memory 19

user interface 20

power supply 21

sensor 23

Entry 230

temperature sensor 231

concentration sensor 232

communication interface 24

code reader 3

Claims (11)

1. An apparatus for roasting partially pre-roasted coffee beans comprising: - a container (1) for holding coffee beans, - an electric heater (13) for heating coffee beans contained in the container, - at least one temperature sensor (23) for measuring the temperature in the container, - at least one sensor (232) for measuring the concentration of at least one volatile organic component (VOC) in the smoke produced in the container, - a control system (180) operable to control the heater, characterized in that the control system is configured to: - apply a roasting recipe dedicated to roasting partially pre-roasted beans comprising at least one temperature profile with respect to time, - measure the concentration of at least one volatile organic component (VOC) in the smoke produced in the vessel during the time the roasting recipe is applied, - detect an increase in the measured concentration as a function of time, characterized in that the control system is also configured to: - stop heating if no increase in the measured concentration occurs after a set reference time t-i. 2. The apparatus according to claim 1, wherein the concentration of at least one component from the list of: CO, CO2, NO, NO2, SO2, formaldehyde is measured. 3. The apparatus according to claim 1 or 2, wherein the reference time t1 is set to 5 minutes. 4. The apparatus according to any one of the preceding claims, wherein the control system is configured to stop the electric heater if the first increase in the measured concentration of the at least one volatile organic component (VOC) occurs before a set reference time to. 5. The apparatus according to the preceding claim, wherein the reference time to is set to 3 minutes. 6. The apparatus according to any one of the preceding claims, wherein the control system is configured to obtain the identification of the type of grains introduced into the container by the user. 7. The apparatus according to the preceding claim, wherein the identification of the grains can be obtained: - by manual input by the user, - from an identification device configured to read identification media from a grain package presented/scanned by the user. 8. A method of roasting coffee beans by using the apparatus according to any one of claims 1 to 7, the method comprising: - apply a roasting recipe dedicated to roasting partially pre-roasted beans comprising at least one temperature profile with respect to time, - measure the concentration of at least one volatile organic component (VOC) in the smoke produced in the vessel during the time the roasting recipe is applied, - detect an increase in the measured concentration as a function of time, - stop heating if no increase in the measured concentration occurs after a set reference time t1. 9. A method according to the preceding claims, wherein the method comprises stopping the electric heater if the first increase in the measured concentration of the at least one volatile organic component (VOC) occurs before a set reference time to. 10. A computer program of a processing unit of a control system of an apparatus for roasting coffee beans comprising a container for holding coffee beans, an electric heater for heating coffee beans contained in the container and at least one sensor for measuring the concentration of at least one volatile organic component (VOC) in smoke produced in the container, the computer program comprising program code and/or program logic that when executed on the processing unit performs the steps of: - apply a roasting recipe dedicated to roasting partially pre-roasted beans comprising at least one temperature profile with respect to time, - measure the concentration of at least one volatile organic component (VOC) in the smoke produced in the vessel during the time the roasting recipe is applied, - detect an increase in the measured concentration as a function of time, - stop heating if no increase in the measured concentration occurs after a set reference time t1. 11. A computer program according to the preceding claim, wherein the program code and/or program logic performs the steps of stopping the electric heater if the first increase in the measured concentration of the at least one volatile organic component (VOC) occurs before a set reference time fe.